Piston-valve cut-off



UNITED STATES PATENT OFFICE.

GORDO?.T MCKAY, OF PITTSFIELD, MASSACHUSETTS.

PISTON-VALVE CUT-OFF.

Specification of Letters Patent No. 6,324, dated April 1'?, 1849.

T0 all whom t may concern Be it known that I, GORDON MGKAY, ofPittsfield, county of Berkshire, and State of Massachusetts, haveinvented a new and useful Cut-Off Valve; and I do hereby declare thefollowing to be a full, clear, and exact description thereof, referencebeing had to the accompanying drawings, whereof- Figure l, is alongitudinal sectional view of the interior of the steam chest, orcylinder, together with a portion 0f the main cylinder of the steamengine; Fig. 2, is a V cross section through the cut-off at the line y,7], Fig. l, and Fig. 3, is a section through the steam passage 79 fromthe steam chest into the main cylinder at the line a: m.

My cut off is constructed on the principle of forming a cylindricalvalve-chest, within which works a piston rod, carrying two pistons, onenear each end, and having the pistons of such thickness as by theiredges to close the steam puts or passages at the two opposite ends ofthe cylinders and to have between the two pistons, a cut-off constructedin such a manner as to be caused to slide with each piston, alternately,through a part of its traverse, and to make a steam joint with the lfaceof the piston while being pushed before it. The two parts of the cut oare packed so as to fit the interior of the valve chest and areconnected together by a pipe or'tube sur rounding the piston rod of thetwo piston valves above described.

From the above description it will appear that my invention may beproperly called a cylindrical-ring cut-ofi'.

By reference to Fig. l, the piston-valve rod will be seen at R; the twopiston valves which Vcorrespond to the two steam passages 79 and 79',and to the two opposite ends of the main working steam cylinder of theengine, are B and B ,-the former, (B,) closing and opening the steampassage 79, and the latter, (B), at the same time, opening and closingthe steam passage 7). s

I is the induction pipe from the boiler bringing the steam into thesteam-chest between the two cut-off valves A and A. These two valves areconnected together by the tube t surrounding the valve-rod B. o is aslot in this tube, through which passes t-he pin e, by means of which,when therod R is made to revolve, on its axis, it will carry the cut-offvalves AA and A round, also,

whereby if it be desired to work the steam at full stroke, the openingsF and F may be brought. to stand opposite to the steam passages 79 and79, and the steam will not then be intercepted by the movements of A andA, but only by the steam valves B and B.

As the positions of the valves and cut-offs are represented in thedrawings, steam may be supposed to be entering by the induction pipe I,passing through the cut-off A by the passages a, a, a, a., (seen in thesection Fig. 2,) to enter the main working cylinder of the engine by thepassage P. The valves and cut offs are suposed to be moving toward theleft, or bottom of the steam chest, the edge j" of the cut-off A beingin c0ntact with the surface of the valve B at g, while the cut-off A hasthe edge j at some distance from the surface g of the piston B. Thelength of time occupied by this space between f and g in passing acrossthe steam passage 79, determines the length of time or v part of thestroke in which steam iiows into the engine cylinder.

lVhen the piston B has moved so far toward the bottom of the steam chestas to bring the edge f of the cut-off A below the steam passage 79, thatpassage will be closed and the steam will be cut off, and will remaincut off from the lower end of the cylinder C while the cut off obstructsits passage, a-nd on the return movement of the valve rod R, the cut-offwill remain in its position, until the piston valve B returns, comes 1ncontact at its face g with the ends f of the cut-off, and moves itupward beyond the passage 79. These two surfaces forming a steam tightjoint, and there being less pressure in the cylinder C than in the steamchest, the line of juncture will remain without powery in the steam toopen the joint.

At Fig. 3 the steam passage is seen to be traversed by the obliquepieces s, e, which I call guard strips, and which cross the steampassage in such directions as to prevent the packing of the piston Bfrom being thrust into the opening of the steam passage and cut away.

Vilhat l claim as my invention and desire to secure by Letters Patent,is-

The cut-o, composed of two cylindrical port-ions or rings working steamtight with the sides of the steam chest and also fitting steam tightwhen brought alternately in pistons and attached to each othersubstantially in the manner herein described.

GORDON MGKAY.

Vitnesses I. A. SEDWIoK, JAMES W. GOWAN.

